In the manufacturing filed of the liquid crystal display technology, since the low temperature poly-silicon, LTPS technology has a better electron mobility, it becomes a new innovation direction of the liquid crystal display. The LTPS technology with the advantage of light, thin, low energy consumption, high brightness and high resolution becomes high-profile.
In the LTPS technology, an a-Si layer is usually formed by the chemical vapor deposition and a crystallization process is performed thereof. The crystallization process is usually performed by Excimer Laser Annealing, ELA technology. The Excimer Laser Annealing, ELA technology is usually melt the a-Si layer to an a-Si liquid by the high temperature of laser. When the a-Si liquid is cool down, the a-Si liquid will depend the crystal unclear in the interface of the solid phase and the liquid phase and a poly silicon, poly-silicon layer is grown.
A crystallization pretreatment to the a-Si layer is usually performed before the ELA crystallization. The pretreatment of the ELA crystallization is usually formed a surface oxidation layer to buffer the energy and form a poly-silicon layer with larger and uniform grain size. Therefore, many technical people focus on the optimization of the technology of the crystallization pretreatment of the ELA to obtain the uniform poly silicon layer.
However, since the difference of the density in the solid phase silicon and the liquid silicon and the stress function in the crystallization process is different. After the crystallization pretreatment of the ELA, even the uniform surface oxidation layer is formed, there are much protrusions in the surface of the interface in the final formed poly-silicon layer as illustrated in FIG. 1, and the later poly-silicon process is influenced. Therefore, a new method to reduce the surface roughness of the low temperature poly-silicon is provided.